The U.S. military has stockpiled thousands of tons of surplus gun propellant materials that are now obsolete and either will not or cannot be used for future applications. It is estimated that the Department of Defense has an inventory of obsolete, excess, and off-spec munitions exceeding 400,000 tons. Reduction of this obsolete surplus is of economic and environmental necessity. However, the traditional means of open burning, open detonation or dumping are not acceptable. They yield no useable materials, contribute to pollution and increase disposal site remediation costs. In particular, these methods result in incomplete mineralization. Complete oxidation of organic materials is difficult and emissions from these methods include hydrogen chloride gas and nitrogen oxides. Further, these methods require further waste disposal. Hazardous solid wastes, that amount to over 12,000 metric tons annually, have to be contained and monitored indefinitely. Further, such methods are not economical. The basic cost of open burning/open detonation is in the region of $900/ton. To this must be added the ongoing cost of maintaining the disposal sites.
Nitrocellulose-based gun propellants and materials containing nitrate ester plasticizers have not previously been considered suitable feedstock for resource recovery and reuse technology because of their long-term instability. Consequently, demilitarization processes for nitrocellulose-based propellants have been directed at benign destruction. Processes involving acid or alkaline hydrolysis of the nitrocellulose and other components are currently being developed.
Various chemical separation methods have been proposed to separate ingredients of explosive materials. For example, U.S. Pat. No. 4,098,627 describes the solvolytic degradation of pyrotechnic materials containing crosslinked polymers. The '627 patent uses a crosslinked polymer, such as polyurethane and the like, as a component which is decomposed by heating to a temperature of up to 160° C. in a solvent comprising an active hydrogen containing compound. However, the process utilizes hazardous solvents such as ethylene diamine, benzene and the like. Further, the process yields no usable products.
Accordingly, what is needed is a cost effective, environmentally friendly and safe method for separating one or more components of gun propellant wastes. It would further be desirable to provide a method wherein the separated components are in a usable/useful form.